Recently, as energy consumption is increased, a solar cell has been developed to convert solar energy into electrical energy.
In particular, a CIGS-based cell, which is a PN hetero junction apparatus having a substrate structure including a glass substrate, a metallic back electrode layer, a P type CIGS-based light absorbing layer, a high-resistance buffer layer, and an N type window layer, has been extensively used.
A plurality of cells are connected with each other in the solar cell and studies have been performed to improve electric characteristics of each cell.